This invention relates to dispensing pump accessories and, more particularly, to accessories for preventing the ingress of air into a dispensing pump and for aiding in aligning the pump prior to a dispensing procedure.
Dispensing pumps are known in the prior art for administering various liquids, including medicants, lotions, oils, perfumes, etc. The majority of dispensing pumps are positive displacement pumps in which the precise size of an administered dose is not considered critical. However, there is a subset of dispensing pumps that satisfy applications where the dose size is considered critical and repeated consistent dosing within narrow tolerances is required. For example, in U.S. Pat. No. 5,881,596 entitled xe2x80x9cMICRODISPENSING OPHTHALMIC PUMPxe2x80x9d which issued on Mar. 16, 1999 to the inventors herein, discloses a pump capable of repeatedly delivering doses as small as 5 microliters. Wherever repeated consistent dosing is required, especially with microdoses, such as that delivered by the pump of U.S. Pat. No. 5,881,596, the ingress of air into the pump mechanism and/or liquid path through the pump may cause dosing irregularity and/or pump stalling. The harmful effects of the ingress of air stem largely from its compressibility. If excessive air is introduced, the pump may require re-priming, which is not desirable, or may be impossible. Even where pumps are insensitive to this problem because the dose volume is sufficiently large that delivery of a dose will cause the an to be purged, the dose volume is nevertheless affected and this is undesirable in certain instances.
A common cause of the ingress of air into a dispensing pump is the exposure of an inlet end of a dip tube to air entrapped in a liquid reservoir. The inlet end is exposed generally because the dispensing pump is oriented in a gravitationally non-upright position and/or a low level of liquid is present in the reservoir.
Separately, with the majority of dispensing pumps, the alignment of the dispensing pump and a target is not critical. There are, nevertheless, devices that require to be carefully aligned with a target prior to delivery of a dose. For example, the pump of U.S.Patent No. 5,881,596 is capable of delivering a dose of ophthalmic medication to an eye. The alignment of the eye, in particular a portion to be treated (e.g., iris, pupil, cornea), with the dispensing pump is an important factor in maximizing the effectiveness of the medication.
It is an object of the subject invention to provide accessories for a dispensing pump which will prevent the ingress of air thereinto.
It is also an object of the subject invention to provide accessories for aiding in the alignment of the dispensing pump prior to actuation of the dispensing pump, and delivery of a dose.
The aforementioned objects are met by a variety of accessories for a dispensing pump.
To prevent the ingress of air into a dispensing pump, in a first embodiment of the invention, a sealed dip tube is provided to replace the liquid reservoir of a dispensing pump. In particular, a dip tube having an elongated member with two ends and an inner passage extending therebetween is provided, in which a liquid supply for the dispensing pump is disposed in the passage. A sealing plug is located in the passage so as to prevent the ingress of air into the liquid. In a preferred embodiment, the sealing plug is slidable in the passage, so as liquid is drawn from the passage, the plug slides behind the liquid as it is drawn and reduces the volume of the passage that is in communication with the dispensing pump. With the arrangement of the first embodiment, the dip tube takes the place of the reservoir, and reduces the likelihood of ingress of air into the pump.
In a second embodiment of the invention, a pliant dip tube is provided to which is mounted an anchor. The pliancy of the dip tube, and the weight of the anchor, cause the dip tube to be responsive to gravitational orientation of the dispensing pump. Thus, for example, where the pump is held upside down (i.e. the nozzle is gravitationally lower than the reservoir), the dip tube is bent by the weight of the anchor to have the inlet thereof be directed downwardly and into communication with the liquid. As such, the likelihood of exposing the inlet of the dip tube to air is reduced. In a normal prior art arrangement, the dip tube is formed stiff and is not weighted. Thus, a prior art dip tube is not generally responsive to shifts in gravitational orientation of the liquid contained in the dispensing pump reservoir. It is also preferred that the anchor have sufficient weight to ensure that the inlet of the dip tube is submerged in the liquid at all orientations of the dispensing pump.
In a third embodiment of the invention, a liquid reservoir is provided which is preferably cup-shaped with a base and an upstanding side wall. A recess is defined in the base of the reservoir, into which an inlet end of a dip tube extends. The dip tube serves to communicate liquid accommodated in the recess with a dispensing pump. Additionally, a semi-permeable membrane extends across the recess. With the dispensing pump in a gravitationally upright position, liquid contained in the reservoir seeps through the membrane to flood the recess. Upon actuation of the dispensing pump, liquid is drawn through the dip tube from the recess. If the dispensing pump is held in a non-upright position, the semi-permeable membrane restricts flow of the liquid out of the recessxe2x80x94albeit the restriction is not absolute, and liquid eventually seeps through the membrane. The restriction of the semi-permeable membrane, however, makes available a liquid supply for a dose of liquid to be administered by the dispensing pump, with the dispensing pump having any orientation, although the supply will be maintained for a limited time (i.e., before all of the liquid seeps out of the recess). With this arrangement, a volume of liquid is maintained, at least for a limited time, about the inlet end of the dip tube in any orientation of the dispensing pump, so as to limit the ingress of air into the dispensing pump.
A safety is provided as a fourth embodiment of the invention. In U.S. Pat. No. 5,881,596, a gravity sensitive failsafe mechanism is disclosed in which a dispensing cap and an actuator coact to prevent actuation of the pump with the discharge aperture being oriented outside a predetermined angular range of operation. Although this arrangement is very effective, the inclusion of the actuator as an additional structural element in a dispensing pump may not be desired. With the fourth embodiment of the subject invention, the safety comprises a safety ball; a blind aperture formed in the underside of a nozzle cap with the blind aperture preferably facing in the actuation direction; and, a conical depression partially in registration with the blind aperture that is defined in the dispensing pump body. The safety ball is disposed in the conical depression, and the conical depression is formed such that when a discharge aperture defined in the nozzle cap is oriented beyond a predetermined angular range of operation, the safety ball is urged out of registration with the blind aperture, and when the discharge aperture is oriented within the predetermined angular range of operation, the safety ball is urged into registration with the blind aperture. Where the safety ball is out of registration with the blind aperture, the safety ball prevents depression of the nozzle cap; conversely, where, the safety ball is in registration with the blind aperture, the nozzle cap may be depressed with the safety ball being received within the blind aperture. The predetermined angular range of operation is selected to increase the likelihood that the inlet end of a dip tube is submerged in liquid in a reservoir of the dispensing pump.
In a fifth embodiment of the invention, a dispensing pump is formed having a pump cylinder disposed partially within a reservoir, with an inlet end of the pump cylinder being in close proximity to the base of the reservoir. The inlet end of the pump cylinder includes an inlet opening which communicates the pump cylinder with liquid contained in the reservoir. No dip tube is used. By locating the inlet end of the pump cylinder in proximity to the base, capillary action of the liquid causes liquid to be drawn to the inlet end/reservoir base interface. To enhance the drawing process, the inlet end may be partially concavely curved away from the base, wherein the concavely curved portion is provided to encourage liquid at the base to feed the pump cylinder equally from all sides. It is also preferred that the pump cylinder be disposed in proximity to a portion of the side wall of the reservoir, and, specifically in proximity to the portion of the side wall located most proximally to the discharge aperture of the dispensing pump. In this manner, the tendency of a party to tilt the dispensing pump forwardly during use is taken advantage of in feeding liquid to the pump cylinder. Also, the pump cylinder/side wall interface allows for capillary action to draw fluid therein. With the dispensing pump in a non-upright position, this capillary action will cause liquid to be drawn up the pump cylinder and to the inlet end thereof. The elimination of the dip tube, and the reliance on capillary action, reduces the likelihood of air being introduced into the dispensing pump.
In a sixth embodiment of the invention, a spectacle frame, that is devoid of lenses, is provided having integrally formed therewith a holder that is formed to engage and hold a dispensing pump. The holder is located so that an engaged dispensing pump will have its discharge aperture aligned with a person""s eye. The holder can be formed to allow for rotation of an engaged dispensing pump, thereby, allowing for a particular area of an eye to be targeted. Once aligned, the dispensing pump is actuated with delivery of a dose of liquid to the intended, aligned area.
In a seventh embodiment of the invention, a mirrored label is disposed about a discharge aperture of a dispensing pump. The mirrored label facilitates alignment of a portion of an eye, that is to receive a dose of liquid, with the discharge aperture of a dispensing pump.